This invention relates generally to a clutch release assembly for selectively coupling a clutch between an engine and a transmission of a motor vehicle.
Clutches for motor vehicles typically include a sleeve connected to a release bearing actuated by a clutch lever or fork. The sleeve engages clutch springs or levers that bias a clutch plate into engagement with a flywheel driven by the engine. The sleeve slides axially along and rotates with an input shaft of the transmission. A clutch release bearing is disposed on the input shaft to engage the sleeve and transmit axial movement from the clutch fork. Typically, the clutch release bearing includes an inner race that rotates with the input shaft and the sleeve, and an outer housing or race that remains stationary relative to the inner race. Typically, the outer housing includes wear pads that are in contact with the clutch fork. The clutch fork is pivotally mounted to a housing and pivoted by an actuator in response to an operator depressing a clutch pedal. The clutch fork pivots to move the clutch release bearing axially along the shaft and thereby open the clutch.
The pivotal motion of the clutch fork in combination with frictional force between the fork arms and wear pads creates an uplift force on the clutch release bearing and sleeve. The uplift force is approximately equal to the coefficient of friction between the fork arms and the pads multiplied by the normal force applied to the arms against the pads. The uplift force presses the sleeve against the input shaft during clutch disengagements to accelerate wear of the shaft and clutch release bearing.
It is becoming increasingly necessary for original equipment manufacturers to construct clutch assemblies that are substantially maintenance free. For that reason it is known to employ rollers on the clutch fork to reduce friction and uplift forces on the clutch release bearing and sleeves. The use of rollers on the fork that actuates the release bearing substantially reduces the friction and thereby the uplift force on the release bearing. However, rollers disposed on the actuation fork must be maintained separately from the clutch release bearing. Typically, the clutch release bearing includes an internal cavity filled with lubricant by way of a grease fitting. The clutch fork has no such configuration; therefore, the rollers on the fork must be lubricated in a separate operation from the clutch release bearing. Typical configurations and locations of the clutch fork increase the difficulty and time required for proper lubrication or replacement of clutch fork mounted rollers.
For this reason it would be desirable to design a clutch release bearing and fork actuation assembly that could further increase the life of the bearing sleeve, eliminate friction that induces uplift and accelerates wear, while providing for routine maintenance and ease of lubrication of the rollers.
An embodiment of this invention is a clutch assembly including rollers mounted on the clutch release bearing in contact with a release fork to substantially reduce wear caused by frictional forces during clutch actuation.
The clutch assembly includes a clutch release bearing moveable along a transmission input shaft and attached to a sleeve. The sleeve moves axially along the input shaft to engage clutch springs or levers that operate to disengage the clutch. The clutch release bearing includes rollers in contact with a clutch release fork. The clutch release fork pivots about an axis in response to movement of an actuator. Pivotal movement of the clutch release fork transmits a force on the clutch release bearing that is normal to the face of contact pads of the clutch release fork. The normal force transmitted to the clutch release bearing includes a non-axial component that can cause premature wear of the clutch release bearing and sleeve. The clutch release bearing of this invention includes rollers disposed at the contact point between the release fork and the clutch release bearing. The rollers eliminates the transmission of non-axial force to the clutch release bearing and to the sleeve, thereby substantially extending the life of the sleeve and clutch release bearing.
In one embodiment of the invention, the rollers rotate about a threaded shaft threadably connected to the clutch release bearing to allow easy change out.
In another embodiment of the invention, the clutch release bearing includes an internal cavity filled with lubricant. Lubricant fills the internal cavity by way of a single grease fitting. Each of the rollers includes a threaded hollow shaft mounted to the clutch release bearing and in communication with the internal cavity. This configuration facilitates lubrication of the rollers through the grease fitting for the internal cavity. Lubricant from the internal cavity flows through the hollow shaft to lubricate the rollers such that the rollers are lubricated during routine maintenance along with the clutch release bearing.
The clutch assembly of this invention includes rollers in contact with a release fork to eliminate axial force on the clutch release bearing and sleeve such that the life of the sleeve and clutch release bearing are substantially extended. Further, the clutch assembly of this invention includes an internal cavity that provides for the common lubrication of the rollers during routine lubrication of the clutch release bearing.